I once wrote a similar method called cleave(). My use case involved a
string-like class (Substr) whose instances could report their position in
the original string. The re module wasn't preserving
my class so I had to provide a different API.
def cleave(self, pattern, start=0):
"""return Substr until match, match, Substr after match
If there is no match, return Substr, None, ''
"""
Here are some observations/questions on Raymond's partition() idea. First
of all, partition() is a much better name than cleave()!
Substr didn't copy as partition() will have to, won't many of uses of
partition() end up being
O(N^2)?
One way that gives the programmer a way avoid the copying would be to
provide a string method
findspan(). findspan() would returns the start and end of the found
position in the string. start >
end could signal no match; and since 0-character strings are disallowed in
partition, end == 0
could also signal no match. partition() could be defined in terms of
findspan():
start, end = s.findspan(sep)
before, sep, after = s[:start], s[start:end], s[end:]
Just a quick thought,
-Tony
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